If you got Omicron post-vaccination, medical experts advise not to rush out for a booster shot

In just a matter of weeks, hundreds of thousands of Canadians likely became infected with the Omicron variant of the coronavirus.

The unprecedented surge of cases has led to cancelled surgeries, staffing shortages in the health-care system and record-breaking hospitalization rates — alongside plenty of less serious bouts of illness, including among those who've been fully vaccinated against COVID-19.

If you're now one of a growing number of people who've been infected post-vaccination, you might be wondering when it's appropriate to get a booster — or if you need one at all.

"People should still get a booster," Dr. Lynora Saxinger, an infectious diseases specialist and associate professor at the University of Alberta in Edmonton, told CBC News. "I think the harder part is, when is the best time to boost?"

Provincial guidance on that timing varies across the country, ranging from Quebec's suggestion to simply wait until your symptoms go away to a recommendation from Ontario's top doctor to hold off for 30 days.

There's no magic number, but the science behind how our immune system works means you might want to wait weeks or even months after an Omicron infection to reap the benefits of a booster shot.

In general, if you're sick, you shouldn't get any type of vaccine, said Alyson Kelvin, a virologist and vaccine researcher at the University of Saskatchewan's Vaccine and Infectious Disease Organization in Saskatoon.

"Your body's immune response to whatever it's fighting is going to be directed toward that pathogen," she explained.

At the same time, your body might not respond as effectively to a vaccine dose, which is meant to trigger your immune system by imitating a threat like the coronavirus. "So this is generally why we should wait some time after being infected to get any vaccine," Kelvin said.

The ideal time to get a booster shot, she said, is when your immune system has calmed down.

Kelvin likened what's happening inside your body to the process of recruiting people for a job: You want highly trained candidates for a specific task, which in this case means fighting off the coronavirus.

"Say you send out a job advertisement, and you get lots of people responding to that job. That's kind of like when you're given an initial vaccine, or you're infected, and your immune response starts to recruit all of these different immune cells," she said.

That's a busy time, but the bulk of those immune cells — or job applicants, shall we say — will eventually tail off. That's when you want another boost to re-engage the immune system, or as Kelvin's analogy goes, another chance to regroup with applicants that are best fitted for the job.

"So definitely, you want to wait till your symptoms clear up, and probably it's beneficial to wait an extra month or a couple of weeks after your initial infection, as you'll have more benefits of that boost," she said.